After a furious struggle in the trenches of the First World War, a British Infantry Company is separated from their regiment. When the British forces try to return to their lines, they come across what appears to be a bombed-out German trench, which has been abandoned except for a few confused German soldiers. The British company fortifies the trench to hold it until reinforcements come, after killing most of the Germans and taking one prisoner. Strange things begin to happen soon, though, as a sense of evil falls on the trench and the British begin to turn on one another.